The present invention relates to a method of producing a scroll type compressor and, more particularly to a method of producing the scroll members incorporated in such a compressor.
The scroll type compressor is a machine incorporating a stationary scroll member and an orbital scroll member which are assembled together to define working fluid chambers therebetween. In operation, the orbital scroll member is driven by a suitable driving means to make an orbital movement with respect to the stationary scroll member so that the volume of the working fluid chambers is progressively changed to compress and discharge the fluid. A typical example of this type of compressor is shown in, for example, U.S. Pat. No. 3,884,599. In general, each of the stationary and orbital scroll members has as its essential parts and end plate and a spiral wrap protruding from one side of the end plate. More specifically, the stationary scroll member for instance has a spiral wrap, end plate and a boss which are formed integrally. A plurality of oil ports are formed in the end plate to open in the flat surface of the latter. These oil ports are in communication with oil passages formed in the end plate to provide passages for the lubricating oil. These oil ports are usually formed by machining from the outer peripheral surface of the end plate for the convenience's sake in the machining. After the machining, suitable plugging members are fitted into the machining ends of the oil ports to close the latter. The scroll type compressor has a bearing portion to which fitted is a bearing metal receiving the crank portion of the drive shaft. A slight space is left in the upper end portion of the bearing. This space is in communication with the aforementioned oil ports. Therefore, the lubricating oil supplied for lubrication of the bearing metal is supplied to the surface of the end plate through the space in the upper end portion of the bearing portion and then through the oil ports.
The above-described stationary scroll member can be formed, for example, by a machining from an integral cast blank. The cast blank, however, generally suffers from inferior dimensional precision so that a long time is required for the machining of the wrap and fine oil ports thereby impractically lowering the efficiency of the work impractically.
U.S. Pat. No. 3,994,635 discloses a method of producing a scroll member, improved to overcome the problems in the conventional production method relying upon machining. According to this method, the spiral wrap is formed as a body separate from the end plate and a fitted in a spiral groove formed beforehand in the surface of the scroll member. The wrap and the end plate are then united with each other by means of, for example, screws. This method, however, is still time consuming due to the necessity for the machining of the spiral groove and oil ports.
Thus, these conventional methods undesirably require long processing time and high production cost. Although other methods such as precision casting, precision forging and so forth are proposed, these methods are still unsatisfactory in that they necessitate the use of special process for attaining the required precision or an additional step of surface treatment.
Accordingly, an object of the invention is to provide a method of producing an improved scroll member of the type in which the end plate and the wrap are formed separately and then assembled together thereby permitting an easy assembling of the wrap and the end plate, as well as high productivity and precision of the scroll member.
In order to overcome the above-described problems of the prior art, methods in which the end plate and the wrap of a scroll member are formed separately and then fixed to each other by making use of a plastic work technique have already proposed by the assignee of the present invention. These methods are disclosed, for example, in Japanese Patent Application Nos. 128358/1978, 76909/1979 and 128584/1978. In these proposed methods, a groove for receiving the wrap is formed in the surface of the end plate by plastic working, and a wrap formed separately from the end plate is fitted in the groove and fixed at its entire periphery by brazing, adhesion, welding such as resistance welding and laser beam welding, diffusion bonding or caluking.
According to the invention, there is provided a method of producing a scroll member in which the end plate and the siral wrap are formed separately, and a discontinuous joining portion is formed either on the end plate or on the lower end of the spiral wrap, so that the end plate and the wrap are joined to each other at the discontinuous joining portion. The joint is achieved preferably by resistance welding. When the orbital scroll member is produced by means of resistance welding, it is preferred to divide the end plate in thickness direction into two parts, namely, an upper half part which is to be joined to the wrap and a lower half part which is to be connected to the boss. The upper half part of the end plate is provided with discontinuous protrusion which easily produces heat during the resistance welding. The discontinuous protrusion is formed preferably by plastic working. On the other hand, the lower half part of the end plate is provided with oil grooves which are formed also preferably by plastic working. The upper and lower half parts of the end plate are then fixed to each other through mutual engagement between locating projections and mating holes formed preferably by a plastic work in their surfaces.
In the production of the stationary scroll member, the end plate and the wrap are formed separately from each other as in the case of the orbital scroll member. In this case, however, the end plate is an integral member from the beginning and is punched out from a sheet blank. The peripheral portion of the sheet blank after the punching out of the end plate constitutes a flange portion of the stationary scroll member which contacts with the end plate of the orbital scroll member.